International Journal of Mosquito Research 2016; 3(4): 39-47

ISSN: 2348-5906 CODEN: IJMRK2 An outbreak investigation of dengue fever in the IJMR 2016; 3(4): 39-47 © 2016 IJMR coastal areas of , Thiruvarur and Received: 07-05-2016 Accepted: 08-06-2016 Thanjavur districts in , during

G Praveen 2012 IDSP, National Centre for Diseases Control, 22-Shamnath Marg, Delhi, India G Praveen, BK Tyagi, Nirmal Joe and Manisha Bias Thakur

B K Tyagi a) Visiting Professor, Punjabi Abstract University, Patiala, Punjab, An outbreak of dengue fever occurred in the coastal Nagapattinam and adjoining Thiruvarur and India Thanjavur districts of Tamil Nadu during late October-early November, 2012. An-depth investigation b) Scientist ‘G’ (Director) & was made into the reasons attributable to the spread of dengue in these districts, both urban and rural Emtd. Director in-Charge, Centre settings, between 23rd and 27th November, 2012. Till 22nd November a total of 299 cases and 2 deaths in for Research in Medical and 612 cases with 3 deaths in Thanjavur district were reported due to dengue. An Entomology (ICMR), 4-Sarojini increased trend in dengue cases was observed from September to November, with all the age groups Street, Chinna Chokkikulam, affected. High entomological indices along with eco-bio-socioeconomic factors such as unprecedented Madurai 625002, TN, India rainfall, construction sites, abandoned houses and boats, tyres and coconut shells were the major reasons for sudden abundance of Aedes mosquitoes. Robust monitoring and surveillance activities, along with Nirmal Joe Regional Office of Health & control measures, by the district authorities kept the disease spread under check by effectively Family welfare, Government of strengthening both case management and laboratory support, on one hand, and regularly organizing India, Chennai interactive co-ordination meetings at all levels to sensitize people through IEC and awareness programmes as well as source reduction of Aedes mosquito breeding. Manisha Bias Thakur Department of Medicine, Keywords: Dengue, outbreak, coastal districts, Nagapattinam, Thiruvarur, Thanjavur, Tamil Nadu Safdarjung Hospital, New Delhi, India Introduction During last two decades dengue, which has lately become a serious public health problem both geographically and in its intensity, emerged as the fastest spreading mosquito-borne viral [1, 3] infection in the world . It is an acute systemic viral disease that has established itself globally in both endemic and epidemic transmission cycles. Dengue virus infection in humans is often unapparent [4] but can lead to a wide range of clinical manifestations, from mild fever to potentially fatal dengue haemorrhagic fever (DHS) and dengue shock syndrome (DSS) [2]. The lifelong immunity developed after infection with one of the four virus types is type- [1, 2] specific and progression to more serious disease is frequently, but not exclusively, [2, 5] associated with secondary infection by heterologous types . Clinical features of dengue virus infection include fever, rash and joint pain [2, 3], which are however common in other certain febrile illnesses and may lead to misdiagnosis and interpretation. The diagnostic methods available also have limitations and a full complement of tests is not feasible in many

healthcare points. Owing to the inherent problems related to definition of these diseases, on one hand, and, since dengue transmission comes in a wide variety of forms, with varying levels of spatial coverage and reliability, on the other, there has been differences in opinion of its global distribution which, considering varied estimates, seems to range from 30% [1] to 54.7% [2] of the world’s population (2.05–3.74 billion) from about 136 countries [1, 6].

Correspondence Ironically, though more than a century has elapsed when dengue virus was first discovered, B K Tyagi there is no effective antiviral agent yet existing to treat dengue infection, nor any licensed Visiting Professor, Punjabi vaccine is available against dengue infection [2]. Because the dengue treatment remains to be University, Patiala, Punjab, supportive, the only way to curb dengue transmission is to focus on the vector control, using India; Emtd. Scientist ‘G’ combinations of insecticides and biological control agents targeting Aedes mosquitoes and (Director) & Director in-Charge, [7] Centre for Research in Medical management of breeding sites . Entomology (ICMR), 4-Sarojini India is among the worst dengue-affected countries in the world, along with Brazil, albeit Street, Chinna Chokkikulam, significant under-reporting [1, 6]. During 2012, dengue resurged almost throughout the country Madurai 625002, TN, India but maximum cases and deaths were reported in Tamil Nadu where some of the coastal districts ~ 39 ~ International Journal of Mosquito Research

were worst-affected [8]. Since this outbreak of dengue cases Material & Methodology occurred severely in those districts which were earlier hit by The worst-affected coastal districts, namely, Nagapattinam, the devastating tsunami during December 2004 and Thiruvarur and Thanjavur, were surveyed from 23rd to 27th government had initiated post-tsunami several re-habilitation November, 2012, along with several senior state and district and vocational schemes, it became all the more important to administrative and health officials, primarily to investigate comprehend the factors behind this upsurge of dengue cases in reasons attributing to the spread of dengue fever in coastal coastal districts [9] ! Tamil Nadu districts (Fig. 1).

Fig 1: Map of peninsular India showing Tamil Nadu with districts ([Note the marked districts of Nagapattinam (#1), Thiruvarur (#2), and Thanjavur (#3)] which were surveyed both virologically and entomologically during a dengue outbreak in November, 2012.

The following methodology was pursued: Observations & Results a) Discussion with District Collector and District Health Nagapattinam distric officials of Nagapattinam, Thiruvarur and Thanjavur (i) Demography, topography and climate districts. Nagapattinam district of Tamil Nadu is located on the shores b) Secondary data mining and analysis of the three districts. of the Bay of Bengal covering an area of 2715.83 sq. km. This c) Visit to hospitals, laboratories and affected villages in the coastal district of Tamil Nadu lies between 10.10° and 11.20° three districts. North latitudes and 79.15° and 79.50° East longitudes. d) Larval and adult collections were done using standard Nagapattinam district was carved out by bifurcating the procedures. The identification was made following the composite Thanjavur district. District Nagapattinam has a keys of Barraud (1936) and Puri (1962). population of 16,14,069 (as per the 2011 census) and is e) The vector incrimination was carried out following the divided in eight taluks, ten blocks and four municipality areas. standard method. The average maximum temperature during the summers remains around 35 °C. The relative humidity of district hovers around 60 to 65%. The average annual rainfall is around 1000mm, notwithstanding majority of precipitation hails during Northeast Monsoon, October-December (Fig. 2). ~ 40 ~ International Journal of Mosquito Research

Fig 2: Mean annual rainfall (2009-2012) for Nagapattinam district.

(ii) First-hand interaction with state and district health and Again on 24th November, to seek appraisal on the dengue administrative authorities scenario in the district with various containment measures To review dengue situation in the state of Tamil Nadu, undertaken by the District Health Authorities, an in-depth particularly the badly affected Nagapattinam, Thiruvarur and discussion was held at the district headquarters of Thanjavur districts, foremost an interactive meeting on Nagapattinam with Mr. Munusamy, District Collector and November 23, 2012, was held with the Health Secretary of Mrs. Asia Mariam, District Revenue officer, Dr P Kannan, Tamil Nadu, Dr. J. Radhakrishnan, IAS, joined by the Director Additional Director (Malaria & Filaria), Dr. V.A. Ralphselvin, of Public Health, Dr. Porkai Pandiyan, and other senior Deputy Director, Nagapattinam, Dr. S. Rajesekar, Deputy officials including Dr. Paranjothy, Director of Medical & Director, Health (On Dengue Special Duty), Dr. Gurunathan, Rural Services; Dr. P Kannan, Additional Director (Malaria & Joint Director Medical and Rural Health Services, Dr. Filaria); Dr. Kolandaiswamy, Additional Director (Primary Kathiresan, Chief Entomologist and Dr. Kumar, Senior Health Centre); Dr. Saravanan, Joint Director (VBCP); Dr. Entomologist at District Collectorate, Nagapattinam. Rukmanandhan Additional Director (Planning); Dr. Raju, Following observations emerged in the meeting: Additional Director (Medical); Dr. Kathiresan, Chief  Even though signs of outbreak began in September, Entomologist and various other entomologists at DMS sporadic cases occurred since January (Table 2). complex, Chennai During the meeting the following  Two deaths in children below 5 years of age were reported observation were made: from Nagapattinam block.  A total of 10,096 cases and 62 deaths due to dengue were  An increased trend in dengue cases was observed from reported in Tamil Nadu till 22nd November 2012, (Table September to mid October 2012 (Fig 2) 1).  Block Nagapattinam, an urban setting, was mostly  All the 32 districts were affected by dengue outbreak, affected (140 cases) having a population of 82,559 and however, Nagapattinam and Thanjavur districts seemed to 16,515 households. have been impacted worst.  Dengue cases were also reported from blocks  While Nagapattinam reported 299 cases and 2 deaths, , Keezhaiyur, Kollidam, away from Thanjavur had reported 612 cases and 3 deaths. the centre of the city.  Spurt in dengue cases was reported during September-  All age groups were affected (Table 3) November.  Entomological indices were found high enough to trigger  Monitoring and surveillance activities, along with spread of dengue infection. containment measures, were carried in both the districts.  Environmental Man-made environmental factors were  Coordination meetings at all levels, sensitization and supporting for Aedes mosquito breeding (Fig 45). awareness programmes and IEC were emphasized in both  Diagnostic treatment facilities were available at district the districts. hospital where sources of mosquito breeding were regularly monitored and reduced, the health department Table 1: Year-wise distribution of dengue cases and deaths in carried out dissemination of educational and information Nagapattinam and Thanjavur districts of Tamil Nadu (2010-2012 (till 22nd Nov.) material.

District District Table 2: Health care delivery infrastructure in district Nagapattinam Tamil Nadu Nagapattinam Thanjavur Year Sl. No. Health Facility No. Deaths Cases Deaths Cases Deaths Cases 1 District hospital 1

2 No. taluk hospital 8 2010 2060 8 17 0 14 0 3 Blocks 10 2011 2501 9 5 0 45 0 4 PHC 51 2012 10096 62 299 2 612 3 5 SC 258 * Source: NVBDCP, Tamil Nadu 6 Villages 434 ~ 41 ~ International Journal of Mosquito Research

(iii) On-spot surveys in affected areas of the District were formed to carry out the antilarval and fogging Hospital Nagapattinam operations.  A total of 4859 fever cases were admitted between 27th (iv) A 6-day working block was organized at the Subcenter August to and 22nd November. level under strict vigilance by both the junior as well as  285 cases were laboratory-confirmed for dengue by IgM the Senior Entomologist. ELISA. (v) District coordination meetings were regularly held at all  A separate adult and paediatric ward was identified in the levels in the district. hospital for admission of dengue patients where all beds (vi) Dengue awareness, sensitization meetings, IEC materials’ were provided with the bed-nets. exhibition were carried out at the community level.  All on-duty physicians and pediatricians were found working at the hospital. (v) Dengue profile during and before outbreak  Blood platelets, plasma cell volume and dengue serology As evident from Table 3, dengue cases surged typically with diagnostics (IgM ELISA) were available in the hospital the onset of South-West Monsoon and the first cases occurred round the clock. in June, which gradually culminated in October. Since October  Blood bank had adequate stock of blood for blood onward the incidence declined steadily. The first, and the last, transfusion, whenever needed. instance of mortality, however, was recorded in September. It is obvious from the Fig. 3 that maximum cases occurred in the (iv) Prevention and control activities undertaken by second and third weeks of October, particularly the former. district health authorities Table 3: Month wise distribution of dengue cases and deaths The district authorities played a key role in containing density in district Nagapattinam (till 22nd Nov., 2012) of the dengue vector, Aedes aegypti, by organizing periodic antilarval spray and fogging activities. These teams adopted a Month Cases Death novel modus operandi by classifying the affected regions into January 3 0 high risk and low risk blocks for administering antilarval and February 0 0 fogging activities. Entomological surveys were carried out March 0 0 during both before and after the outbreak months in the April 2 0 affected blocks so as to deplete any increase in the Stegomyia May 0 0 indices. Some key measures adopted by the health June 7 0 July 2 0 administration included the following: August 6 0 (i) District hospitals of Nagapattinam and Thiruvarur September 61 2 Medical College were well equipped with diagnostic kits October 159 0 such as ELISA, and other necessary infrastructure. November 59 0 (ii) Anti-larval and fogging operations were conducted in all Total 299 2 the 10 blocks. * Source: NVBDCP, Tamil Nadu. (iii) A total of 12 teams in urban and 10 teams in rural areas

Weekwise distribution of Dengue cases reported from Nagapattinam District (27th August -22nd November, 2012)

50 45 40 35 30 25 20 No of cases Noof 15 10 5 0

Oct

Nov

Sep

1 Oct - 7 - Oct 1

3 - 9 Sep 9 - 3

8 - 14 Oct 14 - 8 4 - Oct 29

5 - 11 Nov11 - 5

27 Aug - 2 - Aug27

15 - 21 Oct 21 - 15 Oct 28 - 22

12 - 18 Nov18 - 12 Nov22 - 19

10 - 16 Sep16 - 10 Sep23 - 17 Sep30 - 24 week

Fig 3: Week wise distribution of dengue cases reported from Nagapattinam

District from Aug. 27 to Nov. 22, 2012. Sembanarkoil (57 cases) and Sirkazhi (17 cases) for the same On block-wise analysis of distribution of dengue cases it period. Although all age groups were found affected, became apparent that the maximum cases were reported from nevertheless more cases occurred in early age groups (< 40 the Vadugachery block in the central Nagapattinam town (total yrs) with maximum cases hailing from 5-14 yrs. age group, cases 14 between September and November), where the followed by 0-4, 15-29, 30-44 yrs. age groups, respectively, in outbreak has exacted two deaths as well, followed by that order Table 5 ~ 42 ~ International Journal of Mosquito Research

Table 4: Block wise distribution of dengue cases, district Entomological findings Nagapattinam During entomological surveys made in all the affected areas,

S No. Block September October November larval breeding of the vector, Aedes aegypti, was found quite Vadugachery high considering vector breeding control measures conducted 1 45 (2 deaths) 70 25 (Nagapattinam) on war-footing, with house index (HI) ranging between 5.6 2 Keezhaiyur 3 12 5 and 9.6 and container index (CI) between 5.6 and 10.5 (Fig. 4). 3 Keelvelur 2 3 2 The worst dengue-affected Nagapattinam block lies bordering 4 Thalanayar 0 5 4 the coastal region where the dwellings have been abandoned 5 0 2 2 and locked following the 2004 tsunami. Many of these ravaged 6 Thirumarugal 3 5 2 7 0 1 0 clusters of houses had subsequently given way to the ceiling 8 Kollidam 0 11 3 and become more or less roofless. Such situations, coupled 9 Sembanarkoil 3 39 15 with old and irreparable abandoned boats and construction 10 Sirkazhi 5 11 1 sites, were often found to be breeding heavily with the vector, Ae. aegypti, even long after the rains had ceased to occur. Table 5: Age-wise distribution of dengue cases in Nagapattinam Others breeding habitats for the vector in the block included district unused, stacked tyres, fishing barrels, flexible banners, water Age group Male Female collecting tray under the refrigerator, plastic containers, 0 – 4yrs 28 40 coconut shells etc. (Fig. 4). Due to scarcity of electricity in the 05 -14 yrs 63 66 district, the community has adopted water storing practices 15 – 29 yrs 21 22 such as cement cisterns and ground level sumps. 30 – 44 yrs 10 21

45 – 59 yrs 1 5 60 above 2 0

Fig 4: Larval indices in Nagapattinam block (Nambiyarnagar)

Fig 5: Environmental factors include roofless houses, abandoned boats.

(a) Nambiyarnagar (an urban area under Nagapattinam (b) Keechankupam Village (PHC: Vadavur; SC: municipality) Akkarepetai) Nambiyarnagar ward consisted of 716 households which were PHC Vadavur has eight Subcenters and 24 villages. Village all periodically monitored by municipality and local bodies for Keechankupam has 302 households and is located near antilarval and fogging activities. Daily fever surveillance, Nambiyarnagar. A team consisting of Health Nurse, Health entomological survey and source reduction activities were Inspector supervised the antilarval and fogging activities in the carried out in Nambiyarnagar. village. Daily fever surveillance, entomological survey and source reduction activities were conducted with the help of ~ 43 ~ International Journal of Mosquito Research

community and monitored by the Centre’s team. Houses were unattended during rains which became major breeding sites for surveyed for breeding sites of mosquitoes such as plastic cans, mosquitos. Added to this were the abandoned old boats which vases, urns, underground cement tanks etc. Due to scarcity of too contributed significantly to the breeding of vectors. regular electricity supply, the community adopted the practice Fogging and antilarval activities were carried out but on of storing water. Major occupation of the community was surveying the team found some houses in the community were fishing. Most of the inhabitants were rehabilitated following still found positive for vector breeding (Table 6). the tsunami 2004 and had two-house pattern; one of these, Entomological survey revealed decreasing trend but the generally the newly built house was commissioned by the percentages of the indices are still feasible for dengue Government and the other having been ravished by the transmission (Fig 4 & Fig 6). typhoon of tsunami. The ravaged dwellings were however left

Fig 6: Larval indices in Village Keechankuppam from 30th Oct to 17th Nov 2012

(c) Thalanayar Village (Block Thalanayar; PHC Hospital Nagapattinam during October and November. Thalanayar) Fogging and antilarval activities were carried out but vector IDSP reporting on forms P and L were found properly breeding persisted several houses (Table 6). Entomological executed weekly. The OPD registered 100 cases daily in the survey revealed decreasing trend in view of the repeated PHC. A total of nine cases of dengue were referred to District fogging and antilarval activities (Fig: 7).

Fig 7: Larval indices in village Thalanayar from 16th Oct to 21st Nov, 2012

Entomological Survey and 63.6, respectively. One pool of Ae. aegypti (1 No. male) Larval and adult vector surveys confirmed presence of Aedes and two pools of Ae. vittatus (male 12 and female 12 no.) were aegypti, Ae. albopictus and Ae. vittatus in Nagapattinam found positive for dengue virus using ELISA (Table 7). district, with entomological indices HI, CI and BI as 54.5, 35 ~ 44 ~ International Journal of Mosquito Research

Table 6: Dengue immature survey in the villages of Nagapattinam

House Containers Stegomyia indices Sl No No Examined No of +ve No Examined No of +ve HI CI BI 1 11 6 20 7 54.3 35 63.6

Table 7: Virological surveillance of dengue vectors

Sl No District Total No of pools Pools +ve Pools -ve % 1 Nagapattinam 30 3 27 10

Thiruvarur district  A total of 3136 fever cases were examined during Thiruvarur, earlier a constituent tehsil under Thanjavur November out of which 148 were lab confirmed Dengue district till 1991 and, subsequently under Nagapattinam (IgM ELISA). district up to 1997, finally became annexed to the Thiruvarur  A separate ward each for adults and paediatric were district and designated as its headquarters geographically identified in the hospital for admission of dengue patients. situated strategically between 10 °20' N and 11 °07' S  All beds in the ward had bed nets. latitudes, and 79 °15' E and 79 °45' W longitudes, covering an  Physician and Pediatricians were positioned at the area of 2097.09 sq. km. and a population of 12,61,677 hospital. organized in seven taluks, 10 blocks and four municipalities.  Plasma cell volume and dengue serology kits (IgM The average maximum temperature during the summer ELISA) were available round the clock in the hospital. remains around 39 °C and the relative humidity about 60-65%.  Blood bank had adequate stock of blood for blood The average annual rainfall is app. 967 mm. th transfusion. On 25 November, a discussion was made with the Tiruvarur  National guidelines were followed for case management Medical College authorities including Dr. Mahadevan, Dean, practices. Dr. Chinnappan, Medical Superintendent, Dr. Sundar, RMO,

Dr. Kannapiran, Deputy Superintendent, Dr. Ramamani, Entomological survey Paediatric Chief, Dr. Ashika, HOD Microbiology. Following Larval surveys conducted in Thiruvarur district showed the observations emerged: Stegomyia indices HI, CI and BI as 66.6, 50 and 100,  Thiruvarur Medical College was identified as a Sentinel respectively. A pool of female Ae. albopictus was found Surveillance Hospital for dengue under NVBDCP for positive for dengue virus using ELISA (Table 8,9). tackling the current outbreak.

Table 8: Dengue immature survey in the villages of Tiruvarur

House Containers Stegomyia indices Sl. No No Examined No of +ve No Examined No of +ve HI CI BI 1 3 2 6 3 66.6 50 100

Table 9: Virological surveillance of dengue vector, Ae. Albopictus Mohan, Deputy Director, Thanjavur, Dr. H. Mol Jaw, Joint

Sl No Total No of pools Pools +ve Pools -ve % Director Health Services (Hospital), Dr. P. Srinivasan, MHO, 1 7 1 6 14.2 Thanjavur Muncipality, Mr. N. Ravichandran, Municipal Commissioner, Thanjavur, Dr. Ananthakrishnan, Fever Thanjavur district Management Coordinator, and Dr. Kumar, Senior Thanjavur is situated in the eastern coast of the state of Tamil Entomologist, ZET, Thanjavur. During the discussion the Nadu. Geographically, Thanjavur is placed in between 9 50' following observations emerged: and 11 25' North latitude and 78 45' and 70 25' East longitude.  A total of 612 cases and three deaths of dengue reported District Thanjavur has a population of 23, 64, 714 (as per 2011 from January to November, 2012 (Table 11). census) and is divided in eight taluks, 14 blocks and three  Three dengue deaths were reported from blocks municipalities (Table 10). The average maximum temperature Pattukottai, Peravurani and Thanjavur during June to during the summers remains around 40 °C. The average annual October 2012. rainfall is around 1113 mm.  An increased trend in dengue cases was observed from mid-October to first week of November 2012 (Fig 8). Table 10: Health care delivery infrastructure in District Thanjavur  Block Thanjavur was majorly affected (307 cases and one death) having a population of 5, 10, 411. S. No. Health Facility Quantity 1 Medical college 1  The dengue cases were also reported from blocks namely 2 District Hospital 1 Pattukottai, Orathanadu, Thiruvaiyaru. 3 No. Taluk hospital 8  All age group were affected (Table 12, 13). 4 Blocks 14  Entomological indices were found conducive for dengue 5 PHC 63 spread. 6 Subcenter 309  Man-made environmental factors were supporting for 7 Villages 589 Aedes mosquito breeding (Fig 9).  Diagnostic treatment facilities were available at district th On 26 November 2012, a detailed interactive discussion was hospital; mosquito breeding source reduction and made with the District Collector, Mr. K. Baskaran and Dr. P. Information educational communication were carried out Kannan, Additional Director (Malaria & Filaria), Dr. A. by health department. ~ 45 ~ International Journal of Mosquito Research

Table 11: Month wise distribution of dengue cases and deaths, Table 12: Block wise distribution of dengue cases in Tanjavur district Thanjavur September October November Sl No Blocks Month Cases Deaths Cases Cases Cases January 1 0 1 Thiruvaiyaru 0 31 14 February 4 0 2 Papanasam 0 7 13 March 2 0 3 Kumbakonam 1 14 4 April 2 0 4 Thirupanandal 0 1 0 May 3 0 5 Thiruvidaimaruthur 1 3 3 June 8 1 6 Ammapettai 2 4 10 July 16 0 7 Orathanadu 4 17 17 August 15 0 8 Madukkur 0 1 2 September 40 1 9 Pattukottai 1 17 17 October 309 1 10 Sethubavachatiram 1 1 2 November 212 0 11 Peravurani 6 (1 death) 14 6 Total 612 3 12 Thiruvonam 3 12 9 * Source: NVBDCP, Tamil Nadu. 13 Budalur 0 7 9 14 Thanjavur 21(1death) 180 106

Weekwise distribution of Dengue cases, Thanjavur Distrcit (11 Sep - 23 Nov 2012)

180

160

140

120

100

80

No No of cases 60

40 20

0

29 - 4 Nov 429 -

15 - 21Oct15-

11-16Sep

08 - 1408Oct - 2822Oct -

05 - 1105Nov - 1812Nov - 2319Nov -

17 - 2317Sep-

01 - 07Oct - 01

24 - 30Sep- 24 Weeks

Fig 8: Week-wise distribution of dengue cases reported from Thanjavur district (11 Sep - 23 Nov, 2012)

Table 13: Age-wise distribution of dengue cases in Thanjavur district

Age group (in yrs) Male Female 0 - 4 23 11 05 -14 58 41 15 - 29 125 85 30 - 44 59 69 45 - 59 26 40 > 60 15 9

Fig 9: Anthropogenic environmental factors such as tyres, grinding stones, coconut nutshells

The above pictures from Thanjavur district suggested that dengue transmission. Due to scarcity of electricity in the coconut shells, grinding stones, tyres, water tanks, district, the community has adopted water storing practices underground tanks etc. were the major breeding sites for such as cement cisterns and ground level sumps. ~ 46 ~ International Journal of Mosquito Research

The district authorities and municipal authorities played a key Orathanadu Village (PHC: Thelungankudikadu) role in controlling dengue vector by organizing teams for The PHC Thelungankudikadu had in place both presumptive antilarval and fogging activities. Entomological survey carried and llaboratory forms of IDSP, and the data in P form was out as pre and post survey in the affected blocks revealed entered in the village Orathanadu and transmitted to the district decreasing trend but the percentages of the indices are still on weekly basis. A total of seven cases of dengue were feasible for dengue transmission. reported between September to and November, 2012. On 27th November 2012, the central team did a field visit in House-to-house survey for detecting vector breeding was the affected block. The following affected areas were visited carried out in the village Orathanadu and many households were found positive despite antilarval and fogging operations Thanjavur municipality (Ward No. 21, 20, 36, 38) Urban (Table 14). The record of daily fever surveillance and area antilarval activity of Village Health Nurse and Health The municipality is divided into 51 wards with a population of Inspectors were analyzed. No fever cases were reported during 2-32-361. Survey for Stegomyia indices on vector larval last week. prevalence was carried out in four wards, viz., No. 21-20-36 and 38. House-to-house survey was done to detect breeding, Village Papanadu (PHC: Pappanadu) despite antilarval and fogging activities. Fever cases were House-to-house survey for fever cases and vector breeding reported in Ward No.20 (3 fever cases), N0. 21 (3 cases), No. was made (Table 14). Larval surveys showed the Stegomyia 36 (2 fever cases), and in No. 38 (3 fever cases) on 23rd indices HI, CI and BI as 38.8, 17.4 and 44.4, respectively. One November 2012 who were referred to the district hospital. No pool (five males) of Ae. aegypti was found positive to dengue fever cases were reported on 27th November 2012. virus using ELISA (Table 15).

Table 14: Dengue vector immature survey in the villages of Thanjavur

House Containers Stegomyia indices Sl No No Examined No of +ve No Examined No of +ve HI CI BI 1 14 8 26 10 38.8 17.4 44.4

Table 15: Virological surveillance of dengue vectors World Health Organization, 2009.

Sl No Total No of pools Pools +ve Pools -ve % 3. Tatem AJ, Hay SI, Rogers DJ. Global traffic and disease 1 29 1 28 3.4 vector dispersal. Proc. Natl. Acad. Sci. U. S. A. 2006; 103:6242-6247. Discussion 4. Brady OJ. Refining the global spatial limits of dengue Tamil Nadu is endemic to dengue for decades, but occurrence virus transmission by evidence-based consensus. PLoS of an outbreak following a tsunami (December 24, 2004) in Negl. Trop. Dis. 2012; 6:e1760. [PubMed: 22880140] any district was witnessed for the first time. Tsunami water 5. Halstead SB. Pathogenesis of dengue: challenges to had filled low lying offshore areas which became breeding molecular biology. Science 1988; 239:476-481. sites for various kinds of mosquitoes. Amongst all the districts, 6. Beatty M, Letson W, Edgil D, Margolis H. Estimating the Nagapattinam was worst affected, whereby it attracted the total world population at risk for locally acquired dengue maximum rehabilitation activities subsequently. A hoard of infection; Philadelphia. 2007, 170-257. assistances was provided including housing, boats etc. Tamil 7. W.H.O. Global strategy for dengue prevention and control Nadu in 2012 experienced an unprecedented rain preceded by 2012-2020. World Health Organization, 2012. early monsoon showers [9]. The monsoon hailstorms were so 8. Chandran R, Azeez PA. Outbreak of dengue in Tamil intense that most of the coastal districts, particularly Nadu, India. Current Science 109(1):171-176. Nagapattinam, Thanjavur and Thiruvarur were abundantly 9. Palaniyandi M. The environmental aspects of dengue and inundated in parts [10]. Abandoned boats and households, chikungunya outbreaks in India: GIS for epidemic control. besides, other associated reasons, attracted heavy Aedes International Journal of Mosquito Research. 2014; breeding that resulted in intensive and extensive biting by the 1(2):35-40. vector mosquitoes, particularly Ae. aegypti, though Ae. 10. Indian Council of Medical Research. Annual Report, albopictus was also infrequently encountered. 2005-2006. ICMR, New Delhi.

Acknowledgement In bringing about this investigation the central team had received all kinds of help and assistance from both the administrative and health personnel of the State of Tamil Nadu and to all of them they express their deep sense of gratitude. Thanks are also due to the supportive staff from Centre for Research in Medical Entomology in extending assistance both in field and laboratory works.

References 1. Simmons CP, Farrar JJ, van Vinh Chau N, Wills B. Dengue. N. Engl. J Med. 2012; 366:1423-1432. 2. W.H.O. Dengue: guidelines for diagnosis, treatment, prevention and control. WHO/HTM/NTD/DEN/2009.1.

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